Gelatino silver halide emulsion



Patented May 6, 1930 ..UNITED STATES PATENT OFFICE PAUL C. .SEEL, OFROCHESTER, NEW YORK, ASSIGNOR T EASTMAN KODAK COMPANY, 1 OF ROCHESTER,NEW YORK, A CORPORATION OF NEW YORK GELA'I'INO SILVER HALIDE EMULSION NoDrawing.

This invention relates to gelatino silver halide emulsions.

Light-sensitive emulsions employed as coatings for photographic filmsand plates 5 have generally a low electrical conductivity and tendtherefore to accumulate static charges. This is true particularly offilms Which are subjected during the coating operation to mechanicaltransfer through apparatus. The static charges accumulating on the filmtend to break down with the accompanying formation of sparks. The filmis thus exposed and is sometimes partially spoiled so that sections mustbe removed therefrom.

It is the object of the present invention to provide a light-sensitiveemulsion having a component which increases the electrical conductivityof the coating and thus prevents the accumulation of static charges onthe film. Film coated with such compositions is free from exposed areas,resulting from the discharge of the accumulated static charges.

I have discovered that gelatino silver halide emulsions may be improvedby the inclusion therein of a proportion of ethylene glycol. and thatemulsions including this material are relatively conductive toelectricity so that static charges cannot accumulate on the film Whichsupports the emulsion. Ethylene glycol can be used in substantially allgelatino or collodio silver halide emulsions and is applicable to suchemulsions for the purpose of the invention regardless of the particularcomposition thereof.

As will be understood, such emulsions vary widely in ingredients,proportions, and the treatment to which they have been subjected inpreparation. Typical emulsions are described in the British patent toNewton, No. 23,722 of Nov. 2, 1903; British patent to Swan, No. 2,968 ofJuly 22, 1879; United States patents to Cobenzl, No. 718,312 of J anuary13, 1903; and to Gaedicke, No. 779,777, January 10, 1905; and under theheading, Emulsions in Cassells Cyclopzedia of Photography, published byCassell and Company, Ltd. in 1910. The examples given are merelyillustrative, and changes in the composition of the emulsions do notaffect the invention.

Application filed February 23, 1929. Serial No. 342,320.

100 parts of the emulsion. To obtain the most satisfactory results Iprefer to use approximately .5 parts of ethylene glycol per 100 parts ofthe emulsion, and I have found that this proportion preventssubstantially the accumulation of electrostatic charges and overcomesthe difliculty experienced heretofore in the manufacture of filmsresulting from the exposure of the film as it passes through themachine.

Ethylene glycol of ordinary composition and of technical quality may beused for the purpose of the invention. I can use likewise the polyethylene glycols including diethylene glycol and triethylene glycol.These poly glycols may be employed in substantially the proportionshereinbefore mentioned, and, when used in gelatino silver halideemulsion, they increase the electrical conductivity and prevent theaccumulation of electrostatic charges.

I am aware that glycerine has been added heretofore to gelatino silverhalide emulsions.

Glycerine has, however, a relatively high viscosity and tends to developundesirable stick iness in emulsions. Emulsions containing anyconsiderable proportion of'glycerine are viscous and do not flow freely.It is relatively difiicult therefore to coat the film evenly with suchemulsions. Ethylene glycol and ethylene poly glycols have, on-the otherhand, a viscosity substantially identical with that of Water, so thatthese materials may be added to the emulsions Without substantiallymodifying the viscosity thereof. The glycols have therefore the addedadvantage that they facilitate rather than hinder the coating of thefilm vvith the emulsion.

Emulsions, including glycol or poly glycols ormixtures thereof, can beprepared readily in the simple apparatus which is employed in the normalpreparation of emulsion. The ingredients of the emulsion are mingled inthe usual manner, and the glycol or poly glycols or mixtures thereof, inthe proportions hereinbefore mentioned, are added to and mixedthoroughly with the emulsion which is thereafter coated on the film inaccordance with the customary procedure.

Various changes may be made in the constituents and proportions thereofin the composition and particularly in the proportion of glycol addedthereto without departing from the invention or sacrificing any of itsadvantages.

Having thus described my invention, what I claim as new and desire tosecure by Let ters-Patent is:

1. A gelatino silver halide emulsion containing ethylene glycol.

2. A gelatino silver halide emulsion containing a poly glycol;

3. A gelatino silver halide emulsion containing a poly ethylene glycol.

4. A gelatino silver halide emulsion of high electrical conductivity,containing a glycol derivative, having substantially the viscosity ofwater.

5. A photographically sensitive emulsion including a colloid, sensitivesilver halide saltsand a poly glycol.

6. A photographically sensitive emulsion including a colloid, sensitivesilver halide salts and ethylene gylcol.

Signed at Rochester, New York, this 16th day of Feb., 1929.

PAUL C. SEEL.

